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May 3, 2011 -- The number of people with asthma has been rising in recent years, but CDC researchers say in a new report that they aren’t sure why.

The CDC says that the number of people diagnosed with asthma grew by 4.3 million between 2001 and 2009, when one in 12 Americans were told they had the lung disease. The proportion of people of all ages with asthma in the U.S. increased from 7.3% (20.3 million people) in 2001 to 8.2% (24.6 million people) in 2009.

Costs are rising too, from $53 billion in 2002 to about $56 billion in 2007, for a 6% increase.

“Despite the fact that outdoor air quality has improved, we’ve reduced two common asthma triggers -- secondhand smoke and smoking in general -- asthma is increasing,’’ says Paul Garbe, DVM, MPH, chief of the CDC’s air pollution and respiratory health branch, in a news release. “While we don’t know the cause of the increase, our top priority is getting people to manage their symptoms better.”

Part of the reason, Garbe says, could be better diagnostic methods now in use.

CDC Director Thomas R. Frieden, MD, MPH, says in the news release that asthma is a lifelong disease that kills thousands of people annually and adds billions to the nation’s health care costs.

“We have to do a better job educating people about managing their symptoms and how to correctly use medicines to control asthma so they can live longer, more productive lives, while saving health care costs,” he says.

Preventing and Controlling Asthma

Garbe and Ileana Arias, PhD, principal deputy director of the CDC, spoke at a news briefing after the release an article on asthma in Vital Signs, a report that appears on the first Tuesday of the month as part of the agency’s Morbidity and Mortality Weekly Report.

Both scientists cautioned that asthma incidence is increasing and said that people need to do all they can, such as keeping homes clean and avoiding pollution when possible, to prevent asthma attacks.

They said symptoms can be controlled by correctly using prescribed medicines, such as inhaled corticosteroids, and recommended better education about asthma for the general public and doctors as well.

A higher percentage of children reported having asthma than adults in 2009 -- 9.6% compared to 7.7%. Also, diagnoses were especially high among boys, 11.3%.

The greatest rise in asthma rates was among African-American children, who had a 50% increase from 2001 to 2009, according to the CDC. The highest rate of asthma in 2009 was among African-American children, 17% of whom had asthma.

Annual asthma costs in the U.S. were $3,300 per person between 2002 and 2007.

About two in five uninsured and one in nine insured people with asthma could not afford their prescription medication, the CDC says.

Tips to Reduce Asthma Attacks

The CDC offers a list of recommendations to reduce asthma attacks. These include:

Improving indoor air quality for people with asthma through measures such as smoke-free laws and policies, healthy schools and workplaces.

Teaching patients how to avoid asthma triggers, such as tobacco smoke, mold, pet dander, and outdoor air pollution.

Encouraging doctors to prescribe inhaled corticosteroids for all patients with persistent asthma, and to use a written asthma “action plan” to teach patients how best to manage their symptoms.

Promoting measures that prevent asthma attacks, such as increasing access to corticosteroids and other prescribed medicines.

Encouraging home environmental assessments and educational sessions conducted by doctors, health educators, and other health professionals.

The prevalence of asthma increased went up significantly between 2001 and 2009 in these groups:

Children: from 8.7% to 9.6%

Adults: from 6.9% to 7.7%

Males: from 6.3% to 7.1%

Females: from 8.3% to 9.2%

Whites: from 7.2% to 7.8%

African-Americans: from 8.4% to 10.8%

Hispanics: from 5.8% to 6.4%.

In 2008, CDC says 52.6% of people who had asthma said they’d had an attack in the past year.

Other key findings:

21.8% of people with asthma said they were in fair or poor health, compared to 9.3% who did not have asthma.

In 2008, almost 42% of people with asthma said they missed one or more days of school or work because of asthma in the past year.

People who had an asthma attack missed an average of 4.5 days of school or work per year.

26% of people with asthma reported emergency department or urgent care center visits.

7% were admitted to a hospital for asthma.

Asthma prevalence was higher in the Northeast (9.3%) and Midwest (8.8%) than in the West (7.7%) and South (7.5%).